There are different types of driving mechanisms for electric vehicles and the hub motors are developed to improve the shortcomings of the conventional driving mechanism which require long transmission system and are not suitable for electric wheeled chairs. The conventional hub motors are disclosed in U.S. Pat. No. 3,897,843, 4,346,777, 4,913,258 and 7,719,412. All of the disclosures relate to the use of electric motor directly driving the wheels.
Another conventional hub motor is disclosed in U.S. Pat. No. 6,321,863 and includes an electrical motor received in a hub which is driven by the electrical motor. Nevertheless, the lack of better speed changing system for the conventional hub motor, electrical motor wastes too much electric power and the efficiency of the rotation of the hub is not satisfied. Some alternative inventions for the hub motors are disclosed in U.S. Pat. No. 4,294,138 and 5,273,500. Although a planetary gear system is used in these inventions, the lack of the use of electrical motor makes the hub be inconvenient in practical use.
The applicant of the present invention has devoted a lot of efforts in research and development to improve conventional hub motor. For example, U.S. Pat. No. 6,974,399 owned by the applicant is provided a hub assembly which is driven by an electrical motor with a planetary gear system connected with the electrical motor so as to smoothly and efficiently rotate the hub. U.S. Patent Application 12/896,142 discloses a hub motor which is also owned by the applicant of the present invention and improves shortcomings of the conventional hub motors. However, applicant further improves the present invention which is more advanced than the hub motor mentioned above.